1994 Transport - Having Acceleration Issues

A friend of mine bought a 1994 Pontiac Transport 3.8 not too long ago and it had some issues, he says it sounds like its not accelerating like it should.

When you get to your like cruising speed, he says it sounds like it drops a cylinder and the RPM's drop by about 500, but when you accelerate it comes back.

I think he said he took out the injector and said he couldn't smell any gas just injector cleaner. He told me he thinks its either the injector is burnt out or there is a bad sensor.

So does anyone know what is could be so I can point him in the right direction?

It could also be low compression due to bad rings or a burned/leaking valve (probably on the exhaust side)

Try doing a cylinder leak-down test, to see if they all hold pressure, or, if not, where they are leaking.

Also, try scanning the ECM for codes.

...When you get to your like cruising speed, .. .. the RPM's drop by about 500, but when you accelerate it comes back.
To me, this sounds like the description of the torque converter clutch operation. If RPM drops 500 rpm ands the speed of the car says the same.....this is exactly what you would wnat it to be: TCC engages.
As soon as one hits the throttle, TCC disengages, rpm goes up, normal.